Heat Pump for Heating Swimming Pool Water

ABSTRACT

The invention relates to a heat pump. It relates to a heat pump which, in a primary circuit, comprises a compressor ( 10 ), a condenser ( 12 ) forming a heat exchanger between the refrigerating fluid and the swimming pool water, an expander ( 14 ) and an evaporator ( 16 ) forming a heat exchanger between the external surroundings and the refrigerating fluid. The condenser ( 12 ) comprises two heat exchange circuits and the heat pump comprises a pressure sensor ( 18 ), a member for switching the circulation of the refrigerating fluid between states in which it is circulated in just one or in at least two of the heat exchange circuits, and a member for controlling the switching member according to the value of the signal from the sensor ( 18 ). Application to the heating of swimming pool water.

The present invention relates to a heat pump intended for heatingswimming pool water, and a method for heating swimming pool water.

Heat pumps are thermodynamic systems which comprise a primary circuit ofrefrigerating fluid which comprises a compressor which feeds a condenserforming a heat exchanger between the refrigerating fluid and a heatsource, an expander and an evaporator forming a heat exchanger. The heatexchangers exchange heat with a cold source and a hot source, one ofwhich is an external medium, for example atmospheric air or a flow ofwater.

The document U.S. Pat. No. 5,272,885 describes a heat pump system usedfor the air conditioning of premises. It includes on the one hand anassembly forming a heat pump and on the other hand various usercircuits. In this use, the external medium is constituted by a watersupply unit. In the air heating mode, the apparatus of this documentcools the water of the water supply unit, and in the air cooling mode,the apparatus draws heat from the air of internal air conditioning unitsand heats the water of the water supply unit.

The apparatus is very complicated, since it comprises a number ofcontrol systems: an internal controller with each conditioning unit, adistribution controller, and an external controller. All thesecontrollers control all-or-nothing or gradual regulation (regulation ofthe opening of flow rate regulating valves, variable capacitycompressor, gradual regulation of expander, control of complementaryopening of flow rate regulating valve, etc.). A number of sensors areincorporated in the pump and in each conditioning unit. Two valves canswitch complementary heat exchangers into the circuit.

This apparatus has been described because it shows that simple airconditioning of premises by the use of a heat pump may be verycomplicated, i.e. may require a number of devices having the functionsof detection, regulation, control, etc. and which are subject tobreakdowns, so that a specialist staff member is necessary for thesetting up of such a heat pump. The system should be adapted to permitthe heating of water instead of air conditioning.

The documents GB-2 015 139 and 406 137 describe the switching of heatexchange devices between states providing different heat exchangesurfaces areas.

It is already known to use heat pumps for heating swimming pool water.The heat pumps comprise a primary refrigerating fluid circuit whichcomprises, as indicated in FIG. 1, a compressor 10 which feeds acondenser 12 (which forms a heat exchanger) between the refrigeratingfluid and the swimming pool water to be heated, an expander 14 and anevaporator 16 (which forms a heat exchanger) between the externalmedium, for example the outside air, and the refrigerating fluid.

The characteristics of the exchangers, especially their dimensions, andthe regulation of the expander and of the compressor, are optimised fora specific operating mode. In particular, the condenser is intended topermit the heat pump to provide its maximum power while maintaining anoptimum operating mode from the point of view of the refrigeratingcircuit (pressure and temperature of the refrigerating fluid).

When such a heat pump is used for heating swimming pool water, certainoperating parameters have specific values. Thus, even if the swimmingpool water is very cold, scarcely above 0° C., the user hopes to obtaina temperature generally between 15 and 32° C. Moreover, the watercirculation flow rate of the swimming pool is customarily of the orderof 5 to 15 m³/hr.

It may be imagined therefore that when the thermal exchange is verygreat because the flow rate of water circulating in the condenser isvery high and/or because the water temperature is very low, therefrigerating fluid is cooled to a very great degree, such that thepressure of the refrigerating fluid in the condenser is very low. Theoutput of the heat pump, defined in general by its performancecoefficient, is then reduced and it may even occur that the heat pumpexhibits an operating fault and that it is even damaged.

On the other hand, if the thermal exchange in the condenser is reduced,because the water flow rate is low or because the temperature of theswimming pool water is high, the refrigerating fluid is heated to asignificant degree and causes a pressure increase in the condenser.

The output of the heat pump is then also reduced, the correct operationmay be disturbed, and the heat pump may even be damaged. In particular,beyond a certain pressure, the machine is stopped by a safety pressuresensitive switch.

In order to take this practical situation into account, swimming poolheat pumps generally include a hydraulic branch circuit located upstreamof the heat pump and making it possible to regulate the water flow ratecirculating in the secondary circuit of the condenser (exchanger) of theheat pump, so that the thermal exchange remains optimum and theoperation of the heat pump is satisfactory. The installation shouldtherefore include a regulating device intended to vary the water flowrate circulating in the condenser. Taking into account the water flowrates treated, such a regulating device is tricky to operate and isexpensive. Very often it is simply replaced by a simple manual devicewhich no longer provides any regulating function.

Thus, the known heat pumps present problems linked at least in part tothe defects of complexity, cost and susceptibility to breakdownsindicated previously with reference to the document U.S. Pat. No.5,272,885. These problems represent a serious nuisance in the case ofswimming pools where the owners have no technical knowledge regardingthe operation of heat pumps in general.

The aim of the invention is to solve the problems posed, or at leastreduce their severity, by simplification of the heat pumps for heatingswimming pool water which permits in particular a reduction in cost andsusceptibility to breakdowns.

According to the invention, the problem posed is solved by varying thethermal exchange capacity of the refrigerating fluid heat exchangecircuit of the condensers and not by varying the water flow rate whichcirculates in the condenser. The variation may be effected between onlytwo values, with simple and robust means.

More precisely, according to the invention, when the water flow rate ishigh and the water temperature is low at the inlet of the secondarycircuit of the condenser, i.e. when the secondary circuit of thecondenser has a large capacity for absorbing calories, the heat exchangesurface area of the primary circuit of the condenser is automaticallyreduced.

Conversely, when the water flow rate is reduced and the water is at ahigh temperature at the inlet of the condenser, and therefore has a lowcapacity for absorbing calories, the heat exchange surface area of therefrigerating fluid primary circuit of the condenser is automaticallyincreased.

Thus, the same calorific power can substantially be transmitted to thesecondary circuit of the condenser, and the primary circuit of the heatpump can operate in an optimum mode of pressure/temperature operation ofthe refrigerating fluid.

This result is obtained in practice by the use of a condenser in whichthe primary circuit comprises a plurality of heat exchange circuits,just one or more of which are switched into the circuit. In thecondenser, the refrigerating fluid primary circuit always includes atleast one heat exchange circuit, and at least one other heat exchangecircuit can be switched into the circuit by means of at least oneswitching member, under the control of a control member which isconnected to a sensor for detecting an operating parameter, such as therefrigerating fluid vapour pressure between the compressor and theexpander.

Thus, when the measured pressure increases, the primary circuit of theexpander is increased by switching additional heat exchange circuitsinto the circuit, and the operation is reversed when the measuredpressure decreases.

More precisely, the invention relates to a heat pump intended forheating swimming pool water, of the type which comprises, in a primarycircuit of refrigerating fluid, a compressor, a condenser forming a heatexchanger between the refrigerating fluid and the swimming pool watercirculating in a secondary circuit, an expander, and an evaporatorforming a heat exchanger between the external medium and therefrigerating fluid; according to the invention, the condenser comprisesat least two heat exchange circuits, and the heat pump comprises asensor for detecting a parameter of the operation of the heat pump, atleast one member for switching the circulation of the refrigeratingfluid between a state in which it is circulated in just one of the heatexchange circuits, and a state in which it is circulated in at least twoof the heat exchange circuits, and a member for controlling theswitching member at least according to the value of the signal from thesensor.

Preferably, at least one switching member comprises at least onesolenoid valve.

Preferably, the sensor for detecting an operating parameter of the heatpump detects the pressure of the refrigerating fluid at the highpressure part of the refrigerating circuit, for example between thecompressor and the condenser.

In one embodiment, the heat pump comprises at least two heat exchangecircuits which are disposed in series in the condenser. It may thenfurther comprise a branch circuit with respect to one of the heatexchange circuits.

In another embodiment, the heat pump comprises at least two heatexchange circuits disposed in parallel in the condenser.

The invention also relates to a method for heating swimming pool waterby means of a heat pump according to the preceding paragraphs, whichcomprises the measurement of an operating parameter of the heat pump,the comparison of the measured value of the parameter with a thresholdand, when the parameter exceeds a threshold, the control of theswitching of the refrigerating fluid circulation in a heat exchangecircuit.

Preferably, the comparison with a threshold comprises the use of twodifferent thresholds, depending on whether the parameter increases ordecreases, so that control is obtained with a hysteresis effect.

Other characteristics and advantages of the invention will becomeclearer from the following description of an exemplary embodiment,provided with reference to the appended drawings, in which:

FIG. 1, already described, shows a diagram of a heat pump used forheating swimming pool water;

FIGS. 2 and 3 show two examples of assembly of heat exchange circuits ofthe primary circuit of the condenser of the heat pump;

FIG. 4 is a diagram of a heat pump condenser according to the invention;and

FIG. 5 is a perspective view, with parts removed, of an example of thecondenser shown diagrammatically in FIG. 4.

As FIG. 1 indicates, the compressor 10 brings the refrigerating liquid,in the vapour state, to a high pressure, the pressure beingadvantageously measured by a sensor 18. The refrigerating fluid in thevapour state passes into the condenser 12 and circulates in a primarycircuit part 20.

The primary circuit part 20 of the condenser 12, according to theinvention, may comprise at least two heat exchange circuits 22, arrangedin series, and one of which may have a branch circuit 24 which isswitched into the circuit or not by a solenoid valve 26. When the valve26 is open, the refrigerating fluid circulates in series in the two heatexchange circuits 22, for example two coils, whereas, when the valve 26feeds the branch circuit 24, only the second circuit 22 is fed.

FIG. 3 shows a variant in which heat exchange circuits 22 are arrangedin parallel and each heat exchange circuit, other than the first, isswitched into the circuit or not by the control of an associatedsolenoid valve 28.

The series circuit of FIG. 2, like the parallel circuit of FIG. 3, mayof course comprise a greater number of heat exchange circuits, i.e.coils, as suggested by the interrupted lines.

In addition, it is possible to combine series and parallel devices suchas are illustrated in FIGS. 2 and 3.

The important characteristic of the invention is that, by means of thesolenoid valves 26, 28, the heat exchange capacity of the primarycircuit 20 of the condenser 12 can be varied to a plurality of values sothat the heat pump is always working under its optimum operatingconditions.

FIG. 4 shows an example of a condenser 12 according to the invention. Inthis example, the water passes through an inlet 30 to the vicinity ofthe opposite end of the condenser 12 where it meets the bottom 31 of adeflector 32 which causes the water to return to the same side that itentered, before being deflected again by the end of the outer body 34towards a water outlet 36.

When it circulates between the central pipe and the deflector 32, thewater flows on the surface of a coil 38 forming a first heat exchangecircuit 22. When it circulates between the deflector 32 and the outerwall of the body 34, the water flows on the surface of another coil 40forming a second heat exchange circuit 22 of the primary circuit.

FIG. 4 does not show the connections of the pipes or the solenoid valvepermitting the arrangement in series or in parallel of the two coils 38and 40.

FIG. 5 shows a practical embodiment of the condenser shown in FIG. 4,with the same reference numbers as in the latter.

Although it has been indicated that the variation of the heat exchangesurface area of the condenser was effected by measurement of thepressure at the outlet of the condenser, it is possible to measure otherparameters. In fact, it is generally desirable to monitor on the onehand the pressure and on the other hand the temperature of therefrigerating fluid, at least at one location of the primary circuit. Itis in fact these two parameters which are the most important forobtaining the best performance coefficient of the heat pump. Themeasured parameter may therefore be any combination of parameterscommonly used for this purpose in heat pump technology.

1. Heat pump intended for heating swimming pool water, of the type whichcomprises, in a primary circuit of refrigerating fluid: a compressor(10), a condenser (12) forming a heat exchanger between therefrigerating fluid and the swimming pool water circulating in asecondary circuit, an expander (14), and an evaporator (16) forming aheat exchanger between the external medium and the refrigerating fluid,characterized in that the condenser (12) comprises at least two heatexchange circuits (22), and the heat pump comprises a sensor (18) fordetecting an operating parameter of the heat pump, at least one member(26, 28) for switching the circulation of the refrigerating fluidbetween a state in which it is circulated in just one of the heatexchange circuits (22), and a state in which it is circulated in atleast two of the heat exchange circuits (22), and a member forcontrolling the switching member at least according to the value of thesignal from the sensor (18).
 2. Heat pump according to claim 1,characterized in that the at least one switching member comprises atleast one solenoid valve (26, 28).
 3. Heat pump according to claim 1,characterized in that the sensor (18) for detecting an operatingparameter of the heat pump detects the pressure of the refrigeratingfluid at the high pressure part of the refrigerating circuit.
 4. Heatpump according to claim 1, characterized in that it comprises at leasttwo heat exchange circuits (22) which are disposed in series in thecondenser (12).
 5. Heat pump according to claim 4, characterized in thatit further comprises a branch circuit (24) with respect to one of theheat exchange circuits (22).
 6. Heat pump according to claim 1,characterized in that it comprises at least two heat exchange circuits(22) disposed in parallel in the condenser (12).
 7. Method for heatingswimming pool water by means of a heat pump according to claim 1,characterized in that it comprises: the measurement of an operatingparameter of the heat pump, the comparison of the measured value of theparameter with a threshold and, when the parameter exceeds a threshold,the control of the switching of the circulation of the refrigeratingfluid in a heat exchange circuit (22).
 8. Method according to claim 7,characterized in that the comparison with a threshold comprises the useof two different thresholds, depending on whether the parameterincreases or decreases, so that control is obtained with a hysteresiseffect.
 9. Heat pump according to claim 2, characterized in that thesensor (18) for detecting an operating parameter of the heat pumpdetects the pressure of the refrigerating fluid at the high pressurepart of the refrigerating circuit.
 10. Heat pump according to claim 2,characterized in that it comprises at least two heat exchange circuits(22) which are disposed in series in the condenser (12).
 11. Heat pumpaccording to claim 3, characterized in that it comprises at least twoheat exchange circuits (22) which are disposed in series in thecondenser (12).
 12. Heat pump according to claim 2, characterized inthat it further comprises a branch circuit (24) with respect to one ofthe heat exchange circuits (22).
 13. Heat pump according to claim 3,characterized in that it further comprises a branch circuit (24) withrespect to one of the heat exchange circuits (22).